It is known practice to dye keratin fibers, and for example, human hair, with dye compositions comprising oxidation dye precursors, such as ortho- or para-phenylenediamines, ortho- or para-aminophenols, and heterocyclic compounds, which are generally referred to as oxidation bases. These oxidation bases, are colorless or weakly colored compounds which, when combined with oxidizing products, can give rise to colored compounds by a process of oxidative condensation.
It is also known that the shades obtained with these oxidation bases can be varied by combining them with couplers or coloration modifiers, the latter being chosen, for example, from meta-diaminobenzenes, meta-aminophenols, meta-diphenols, and certain heterocyclic compounds such as indole compounds.
The variety of molecules used as oxidation bases and couplers makes it possible to obtain a wide range of colors.
It is desirable for the “permanent” coloration obtained by means of these oxidation dyes to satisfy a certain number of requirements. For example, such a coloration typically may have at least one of the following properties: no toxicological drawbacks, allows shades of the desired intensity to be obtained, and shows good resistance to external agents such as light, bad weather, washing, permanent waving, perspiration and rubbing.
Other properties that may be possessed by such dyes include: allowing white hairs to be covered and being as unselective as possible, i.e., allowing the smallest possible differences in coloration to be produced over the entire length of the same keratin fiber, which may be differently sensitized (i.e. damaged) between its end and its root.